Method of separating fiber tows

ABSTRACT

Methods and systems for separating fiber tows (e.g., carbon tows) are disclosed. The system may include a chamber defining first and second openings and a hollow interior therebetween. The first opening may be configured to receive a fiber tow and the second opening may be wider than the first opening. A vacuum source communicating with the chamber may be configured to reduce an air pressure in the hollow interior and expand the fiber tow. The method may include pulling a fiber tow having an initial width into a first chamber opening, through a hollow chamber interior, and out of a second chamber opening. Air pressure within the hollow chamber interior may be reduced to separate the fiber tow residing in the hollow chamber interior into an expanded fiber tow having a width greater than the initial width. The disclosed methods may separate the tow more gently than mechanical methods.

TECHNICAL FIELD

This disclosure relates to a method of separating fiber tows, forexample, carbon fiber tows.

BACKGROUND

Increased fuel economy is an important goal for vehicle manufacturers.The desire for improved fuel economy may be driven by fuel costs,emissions standards (e.g., for carbon dioxide), improved range, or otherreasons. One approach to improving fuel economy is using lightweightmaterials to reduce vehicle weight. Carbon fiber is a low-densitymaterial with good mechanical properties. Currently, carbon fiber isgenerally used in applications such as aerospace, wind energy, sportinggoods, and high-end vehicles. These applications are generally lower involume and higher in price compared to high-volume vehicles.Implementation of carbon fiber into high-volume, non-luxury vehicles inthe auto industry poses some challenges.

One of the challenges is developing low-cost processing technology forhigh-volume production. A sheet molding compound (SMC) process has beenused to manufacture glass fiber reinforced parts, such as decklids,hoods, bumpers, and others. However, the same SMC process may not besuitable for carbon fibers due to differences in the physical propertiesof the two fiber types. Carbon fibers may be smaller in diametercompared with glass fibers (e.g., twice as small), which can make carbonfiber tows difficult to separate. In addition, sizing materials that maybe coated on the carbon fiber surface can make carbon fibers tend toagglomerate.

SUMMARY

In at least one embodiment, a fiber tow separating system is provided.The system may include a chamber defining first and second openings anda hollow interior therebetween; the first opening configured to receivea fiber tow; the second opening being wider than the first opening; anda vacuum source communicating with the chamber and configured to reducean air pressure in the hollow interior and expand the fiber tow.

A sealing member may extend around the first opening and be configuredto engage the fiber tow. The sealing member may be made of rubber. Asealing member may extend around the second opening and be configured toengage the expanded fiber tow as it exits the second opening. In oneembodiment, the second opening is at least 50% wider than the firstopening. In another embodiment, the second opening is at least 200%wider than the first opening. The first opening may have a width of 3 to20 mm and the second opening may have a width of 5 to 75 mm. In oneembodiment, a width of the hollow interior continuously increases fromthe first opening to the second opening. One or more hoses may becoupled to the chamber and the vacuum source. In one embodiment, thevacuum source is configured to reduce the air pressure in the hollowinterior to 1 torr or less.

In at least one embodiment, a method of separating fiber tows isprovided. The method may include pulling a fiber tow having an initialwidth into a first chamber opening, through a hollow chamber interior,and out of a second chamber opening; and reducing an air pressure withinthe hollow chamber interior to separate the fiber tow residing in thehollow chamber interior into an expanded fiber tow having a widthgreater than the initial width.

In one embodiment, the second chamber opening may be wider than thefirst chamber opening and reducing the air pressure within the hollowchamber interior may separate the fiber tow into an expanded fiber towhaving a width that is substantially the same as a width of the secondchamber opening. A sealing member may extend around a perimeter of thefirst chamber opening and pulling the fiber tow into the first chamberopening may form at least a partial seal between the fiber tow and thesealing member. A sealing member may extend around a perimeter of thesecond chamber opening and pulling the fiber tow out of the secondchamber opening may form at least a partial seal between the expandedfiber tow and the sealing member.

In one embodiment, the reducing step may include reducing the airpressure within the hollow chamber interior to 1 torr or less. Thereducing step may include reducing the air pressure within the hollowchamber interior using a vacuum hose coupled to the hollow chamberinterior and to a vacuum source. In one embodiment, the reducing stepincludes reducing the air pressure within the hollow chamber interior toseparate the fiber tow into an expanded fiber tow having a width that isat least 100% greater than the initial width. The method may furtherinclude chopping the expanded fiber tow into a plurality of expandedfiber tow segments and incorporating the expanded fiber tow segmentsinto a sheet molding compound material. In one embodiment, the fiber towis a carbon fiber tow.

In at least one embodiment, a method of separating a carbon fiber tow isprovided. The method may include pulling a carbon tow having an initialwidth into a first chamber opening, through a hollow chamber interior,and out of a second chamber opening; and reducing an air pressure withinthe hollow chamber interior to 100 torr or less to separate the carbontow residing in the hollow chamber interior into an expanded carbon towhaving a width at least 50% greater than the initial width.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example of a carbon fiber tow;

FIG. 2 is a top view of a fiber tow separation system, according to anembodiment;

FIG. 3 is a top view of a fiber tow entering and being separated by afiber tow separation system, according to an embodiment;

FIG. 4A is a front end view of a fiber tow separation system form,according to an embodiment;

FIG. 4B is a rear end view of a fiber tow separation system form,according to an embodiment;

FIG. 4C is a side view of a fiber tow separation system form, accordingto an embodiment;

FIG. 5A is a top view of a fiber tow separation system form, accordingto an embodiment;

FIG. 5B is a top view of a fiber tow separation system form, accordingto another embodiment;

FIG. 5C is a top view of a fiber tow separation system form, accordingto another embodiment; and

FIG. 6 is a schematic of a fiber tow chopping system, according to anembodiment.

DETAILED DESCRIPTION

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention that may be embodied in variousand alternative forms. The figures are not necessarily to scale; somefeatures may be exaggerated or minimized to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the present invention.

As described in the Background, the SMC process used to manufactureglass fiber reinforced parts may not be suitable for producing carbonfiber reinforced parts. The bundling of carbon fibers can cause issuesin the SMC process. For example, it may be difficult for resin to wetout (e.g., fully impregnate) the carbon fibers and the fibers may notflow well during molding. These issues may result in relatively lowsurface contact between the carbon fibers and the resin. Due to theseissues, carbon fiber reinforced SMC parts have not yet met the requiredmechanical performance for some applications. An economical andeffective method to improve the carbon fiber separation in the carbonfiber SMC process may improve final part performance.

An example of a partially separated carbon tow 10 is shown in FIG. 1. Acarbon tow is a bundle of individual carbon fiber filaments or strands12 that form a larger strand. Carbon tows may be woven together intocloth or a weave. Carbon tows may be defined or classified by size, suchas 3 k, 6 k, 12 k, 24 k, 36 k, 48 k, or higher, where the “k” representsa thousand filaments. For example, a 12 k carbon tow may include 12,000carbon filaments. Carbon tows may come in a variety of sizes, and thesize chosen may depend on the application. The diameter of the filamentsmay also vary depending on the desired properties or the application.The diameter of the filaments may vary, for example, from 1 to 25microns, or sub-ranges therein, such as 5 to 15 microns or 5 to 10microns.

The production of carbon fiber and carbon fiber tows is known in theart, and will not be described in detail. In general, the production ofcarbon fiber tows includes the steps of polymerization, spinning,oxidation, carbonization, and surface treatment. However, there aremultiple methods for producing carbon fiber tows and any method may becompatible with the present disclosure. Polymerization generallyincludes converting a polymeric feedstock (e.g., precursor) into amaterial that can be formed into fibers. In general, fibers may beformed from polyacrylonitrile (PAN), made from acrylonitrile, howeverfiber may also be formed from other precursors such as rayon orpitch-based precursors. The precursor may be in a powder form and may bedissolved in a solvent, such as an organic or aqueous solvent, to form aslurry.

Fibers may be formed by spinning, such as wet spinning. The slurry maybe immersed in a coagulant and extruded through holes in a bushing orspinneret having a number of holes that matches the desired filamentcount of the tow. The wet-spun fiber may be washed, dried, andstretched. While wet spinning is one approach to forming carbon fibers,others known in the art may also be used. After drying, the fibers maybe wound, for example, onto bobbins.

The fibers, which may be wound or rolled, may then be inserted or fedthrough one or more ovens during the oxidation step. The oxidationtemperature may range from about 200° C. to 300° C. The process maycause the polymer chains to crosslink and increase in density. Theoxidized fibers may contain about 50 to 65 percent carbon moleculesafter oxidation, with elements such as hydrogen, nitrogen and oxygenforming the balance.

In the carbonization step, the fibers are heated again but in an inertor oxygen-free atmosphere. Without oxygen, non-carbon molecules areremoved from the fibers. The carbonization step may include heating atone or more temperatures, for example, a first, lower temperature and asecond, higher temperature. The temperatures may range, for example,from 700° C. to 1500° C. The fibers may held in tension throughout theproduction process. During carbonization, crystallization of the carbonmolecules occurs and the finished fiber may be more than 90 percentcarbon.

After carbonization, the fibers may receive a surface treatment and/or acoating named sizing. The surface treatment may include pulling thefiber through an electrochemical or electrolytic bath that containssolutions to etch or roughen the surface of each filament. A coating,generally called sizing, may then be applied to the fibers. The sizingis intended to protect the carbon fibers during handling and processingso that the fiber surfaces are not scratched or damaged. After thesizing is applied and has dried, the fiber tows are generally bundled orwound-up for later use (e.g., on bobbins).

In order to form a carbon fiber reinforced SMC component, it may bebeneficial to separate or split the carbon fiber tow (e.g., the finishedtow) into individual filaments. This may improve wet-out of thefilaments and increase the surface area contact between the fibers andthe resin, leading to improved properties of the SMC component (e.g.,load transfer). Previous approaches to splitting the tows have includedmechanical methods to physically separate the fiber filaments. Thesemethods can damage the fiber surface during the process and generallyonly split large fiber tows into relatively smaller fiber tows.

With reference to FIGS. 2-5C, embodiments of a method for separating orsplitting fiber tows are shown. In addition, embodiments of a system forsplitting fiber tows are shown and described. While the embodiments maybe described using carbon tows as an example, other types of fiber towsmay be used in the methods, systems, and components and such use iscontemplated herein. For example, glass fiber tows, ceramic fiber tows,polymer fiber tows, or others may be used.

An alternative to mechanically separating the filaments of a tow, forexample, by using rollers with projections extending therefrom orapplying high pressure fluid to the tow has been discovered. It has beenfound that reduced or low pressure may be used to separate the filamentsin a more gentle fashion, without causing as much surface damage orbreakage to the filaments. With reference to FIG. 2, a system 20 isshown for separating the filaments of a fiber two to increase the widthof the tow and the spacing between the filaments of the tow.Accordingly, the total surface area of the tow may be increased, whichmay allow better resin wet-out and improved surface contact between thecarbon fibers and the resin during the production of a composite.

In at least one embodiment, the system 20 may include a chamber (e.g.,vacuum chamber) or form 22. The form 22 may be referred to as a towexpander or separator. The form 22 may have a body 24, which may definea hollow interior 26. The body may be formed of a rigid material that isable to withstand a substantial pressure difference (e.g., as describedbelow) between the hollow interior 26 and the exterior of the form 22(e.g., the atmosphere). For example, the body 24 may be formed of ametal or a rigid plastic. The walls of the body 24 defining the hollowinterior 26 may be smooth (e.g., low surface roughness) in order toprevent damage to the fiber tow as it passes through. For example, ifthe body 24 is metal, it may be polished. The form 22 may have a firstend 28 and a second end 30. The first end 28 may be a tow receiving orentering end, while the second end 30 may be a tow exiting end. Thefirst end 28 may define a first opening 32 that is configured to receivea tow. The tow may be received by the first opening 32, pass or extendthrough the body 24 and exit from a second opening 34 defined by thesecond end 30.

The first end 28 may include a sealing member 36 extending around atleast a portion of the first opening 32. In one embodiment, the sealingmember 36 extends around an entire perimeter of the first opening 32.The sealing member 36 may be flexible such that it may conform to theshape of the tow when the tow passes through the first opening 32. Thesealing member may be formed of a rubber or other elastomeric material.In at least one embodiment, the first opening 32 may be sized to have asame or similar shape as the cross-section of a fiber tow. Fiber towsmay generally have a rectangular or roughly rectangular cross-section,having a relatively large width and a relatively small height.Accordingly, the first opening 32 may also have a rectangular or roughlyrectangular cross-section, having a relatively large width (W1) and arelatively small height (H1) with dimensions that are the same orsubstantially the same as a fiber tow. For example, the tow width mayoccupy from 95 to 100% of the width (W1), such as 97 to 100% or 99 to100%. Therefore, the dimensions of the first opening 32 may varydepending on the size of the tow. For example, a 12 k tow may have asmaller width than a 48 k tow, therefore, a form 22 for a 12 k tow mayhave a first opening 32 that is smaller than a form 22 for a 48 k tow.

Accordingly, when a tow enters and extends through the first opening 32having dimensions the same or very similar to the tow, the sealingmember 36 may conform to the tow to form at least a partial seal withthe tow. As used herein, a partial seal may refer to a seal that allowssome airflow and/or balancing of pressure but that still allows asignificant differential in pressure on either side of the seal to begenerated and maintained. For example, if the pressure outside of theform 22 is at ambient pressure (e.g., 1 atm or 760 torr) then thepartial seal may allow for an internal pressure within the body 24 ofsignificantly less than ambient pressure (e.g., less than 0.5 atm or 380torr). In contrast, if the first opening 32 was larger than the tow by asubstantial amount, then there may be no seal formed and no significantpressure differential may be maintained. In other embodiments, acomplete seal or a nearly complete seal may be formed between the towand the first opening 32.

The second end 30 may also include a sealing member 38 extending aroundat least a portion of the second opening 34. The sealing member 38 maybe formed of the same or similar materials to the sealing member 36(e.g., rubber or elastomer). In one embodiment, the sealing member 38extends around an entire perimeter of the second opening 34. The sealingmember 38 may be flexible such that it may conform to the shape of theexpanded or separated tow when the tow passes through the second opening34 and exits the form 22. When a tow exits through the second opening34, the sealing member 38 may conform to the expanded/separated tow toform at least a partial seal with the expanded/separated tow. The termpartial seal may have a similar meaning to that described above. Inother embodiments, a complete seal or a nearly complete seal may beformed between the expanded/separated tow and the second opening 34.

As described above, fiber tows may generally have a rectangular orroughly rectangular cross-section, having a relatively large width and arelatively small height. The second opening 34 may also have arectangular or roughly rectangular cross-section, having a relativelylarge width and a relatively small height. However, the dimensions ofthe second opening 34 may be different than the tow's originaldimensions (e.g., just prior to entering the first opening 32). Asdescribed in greater detail below, the tow may be expanded or separatedwithin the form 22 such that it has a greater width when it exits theform 22 through the second opening 34. Therefore, the dimensions of thesecond opening 34 may be configured to have a larger width (W2) than theoriginal tow. The expanded tow may have a width that is the same orsubstantially the same as the width (W2) of the second opening 34 whenit exits the second opening 34. For example, the expanded tow width mayoccupy from 95 to 100% of the width (W2), such as 97 to 100% or 99 to100%.

The width of the second opening 34 may correspond to a desired expandedtow width. The expansion or separation of the tow may be defined interms of percent expansion or separation. For example, the separated towmay have a width that is at least 25% larger than the original tow width(e.g., 1.25× the original width). In one embodiment, the separated towmay have a width that is at least 50%, 100%, 150%, 200%, 250%, or 300%larger than the original tow (e.g., 1.5×, 2×, 2.5×, 3×, 3.5×, or 4× theoriginal width). Even greater expansion may be possible, however, maynot be required for sufficient improvement in resin wet-out.

In addition to the second opening 34 being wider than the original tow,it may also have a height (H2) that is smaller than the original tow. Asthe separated tow becomes separated or expanded in the width direction,it may become shorter in height. Accordingly, the second opening 34 mayhave a height that is smaller than the original tow. The reduction isheight may or may not match the increase in width. For example, if thesecond opening 34 is 100% larger in width (2×), it may be 50% of theoriginal height (½×). However, a 1:1 ratio in change is not necessary.In some embodiments, the reduction in height may be less than theincrease in width (e.g., 2×width, ¾× height).

A fiber tow, for example a carbon fiber tow, may have a range of widthsdepending on the tow and/or filament size. In one embodiment, the towmay have a width of 3 to 25 mm, or any sub-range therein, such as 3 to20 mm, 3 to 15 mm, 5 to 15 mm, 5 to 10 mm, 10 to 15 mm, 7 to 13 mm, orothers. Accordingly, the first opening 32 may have a width that is thesame or similar to the tow width (e.g., same ranges as above).Similarly, a fiber tow may have a range of heights depending on the towand/or filament size. In one embodiment, the tow may have a height orthickness of 10 to 250 μm, or any sub-range therein, such as 25 to 250μm, 25 to 200 μm, 25 to 150 μm, 50 to 250 μm, 50 to 200 μm, 50 to 150μm, 50 to 100 μm, 25 to 75 μm, or others. Accordingly, the first opening32 may have a height that is the same or similar to the tow height(e.g., same ranges as above).

As described above, the second opening 34 may have a width that islarger than the first opening 32 and larger than the original tow width.For example, it may be 50%, 100%, 150%, 200%, 250%, or 300% larger thanthe original tow. Accordingly, the width of the second opening 34 may be50%, 100%, 150%, 200%, 250%, or 300% larger than the values describedabove for the width of the first opening 32. In one embodiment, thewidth of the second opening may be from 5 to 100 mm, or any sub-rangetherein, such as 5 to 75 mm, 10 to 100 mm, 10 to 75 mm, 10 to 50 mm, 15to 75 mm, 15 to 50 mm, 10 to 30 mm, 15 to 30 mm, or others. As describedabove, the second opening 34 may have a height that is the same orsmaller than the first opening 32. Accordingly, the second opening 34may have a height that is the same or smaller than the values describedabove for the first opening.

As described above, the disclosed system may use low or below ambientpressure to expand and/or separate the fiber tow. In at least oneembodiment, the system may include one or more (e.g., a plurality) ofvacuum hoses or tubes 40 connected or coupled to one or more vacuumsources 42, such as vacuum pump(s). The vacuum hoses may attach to theform 22 at ports 44. For example, there may be a port 44 for each vacuumhose 40. The vacuum hoses 40 may couple or attach to the ports 44 in anysuitable manner, such as through a threaded coupling, a snap-oncoupling, adhesive, fasteners, interference/friction fit, or othermethods. The attachment may be permanent or detachable/releasable. Inone embodiment, there may be one or more vacuum hoses 40 connected toeach of the top and bottom of the form 22 (e.g., the larger sides, ortrapezoidal sides).

In operation, the vacuum source 42 may lower the pressure within thehollow interior 26 of the body 24 of the form 22 by removing air via thevacuum hoses 40 and ports 44. The pressure may be reduced while a fibertow is being pulled into the first opening 32, through the body 24, andexiting from the second opening 34. Accordingly, the fiber tow may be ata relatively high air/atmospheric pressure just prior to entering theform 22 (e.g., standard atmospheric pressure—1 atm or 760 torr). Whenthe tow enters the hollow interior 26 of the form 22, which is at alower pressure, the filaments of the fiber tow may be urged or driven toexpand or separate by the reduced pressure. The filaments of the tow mayexpand to the size/width of the cross-sectional area of the body 24 as aresult of the reduced pressure. Accordingly, when the tow exists throughthe wider second opening 34, the tow may have expanded to the width ofthe second opening 34, or close thereto.

The strength of the vacuum may be any reduced pressure sufficient toseparate and expand the fiber tow (e.g., to the size of the hollowinterior and/or second opening 34). The magnitude of the pressurereduction required may depend on factors such as the size of the tow(width and/or number of filaments), the size of the second opening(e.g., amount of desired expansion), the length of the body 24 of theform 22, the speed of the fiber tow, or others. In at least oneembodiment, the pressure within the body 24 may be reduced to half orless than the ambient or exterior pressure. For example, if the exteriorof the form 22 is at standard atmospheric pressure of 1 atm or 760 torr,the pressure within the body 24 may be reduced to 0.5 atm (380 torr) orless. In one embodiment, the pressure within the body 24 may be reducedto 100 torr or less, such as 10 torr or less, 1 torr or less, 10⁻¹ torror less, or 10⁻² torr or less. Even lower pressures may also be used,however, they may be unnecessary to expand the tow to the extendnecessary.

With reference to FIG. 3, a schematic of a fiber tow 50 being expandedby a form 52 is shown. The fiber tow 50 has an initial width 54 prior toentering the form 52. Within the form 52, the reduced pressure may causethe tow 50 to expand and/or separate. The tow may expand to the size ofthe form 52. Accordingly, the width of the form 52 may increase from theside where the tow enters to the side where the tow exits, which mayallow the tow to expand as it extends through the form 52.

In the embodiment shown, the width of the form 52 continuously increasesfrom one side to the other, which may allow the tow to similarlycontinuously increase in width. However, the form need not continuouslyincrease in width, as long as the exit is larger than the entrance. Forexample, the width of the form 52 may increase in steps, wherein thewidth is constant for a certain length and then increases, then isconstant for a certain length, and increases again, etc. The width ofthe form 52 may increase linearly (e.g., at a constant rate), as shown,or it may increase at a changing rate, such as parabolic, exponential,or other rates. The tow 50 may expand or separate to fill orsubstantially fill the width of the form 52 along its length, regardlessof the shape of the form 52. When the tow 50 exits the form 52, it mayhave an expanded or separated width 56 that is larger than the initialwidth 54. The magnitude of the increase may depend on the geometry ofthe entrance and exit, as described above.

To initiate the process shown in FIG. 3, the tow 50 may be initiallymanually, mechanically, or otherwise spread to the separated width 56.This may cause the tow to fill or substantially fill the opening in thesecond end, which may allow the sealing member around the second openingto form at least a partial seal with the separated tow. Once the atleast partial seal is formed, the vacuum source and hoses may reduce thepressure within the form 52. The reduced pressure may then separate orexpand the tow without further manual or mechanical separation as thetow is pulled through the form 52.

With reference to FIGS. 4A-4C, example end views and a side view of aform 60 are shown, according to an embodiment. FIG. 4A shows a front endview showing a first end 62 of the form 60 including a first opening 64and a sealing member 66 surrounding the first opening 64. FIG. 4B showsa back end view showing a second end 68 of the form 60 including asecond opening 70 and a sealing member 72 surround the second opening70. As shown, the first opening 64 has a smaller width than the secondopening 70, which may allow the tow to expand from when it enters thefirst opening 64 to when it exits the second opening 70. The firstopening 64 may have a larger height than the second opening 70, asshown, however, it is not required. FIG. 4C shows a side view with thefirst end 62 on the left and the second end 68 on the right. One of twoopposing side walls 74 is shown. If the height of the second opening 70is smaller than the first opening 64, then the side walls 74 may have adecreasing height from the first end 62 to the second end 68.

With reference to FIGS. 5A-5C, example top and/or bottom views of theform 60 are shown, according to several embodiments. FIG. 5A shows aform 60 where the width increases at a constant rate from the first end62 to the second end 68. The top/bottom of form 60 may have atrapezoidal or truncated triangle shape. FIG. 5B shows a form 60 wherethe width increases for a certain length, then remains constant for alength, and then repeats. While two regions of increasing width areshown, there may be more. FIG. 5C shows a form 60 where the widthincreases at a changing rate from the first end 62 to the second end 68(e.g., curved or parabolic). The top/bottom of the form in FIG. 5C maybe referred to as bell-shaped. The length of the form 60 from the firstend (entrance) to the second end (exit) may vary depending on the shapeof the form and the rate of change in the width of the form. A form witha more gradual width increase may be longer and a form with a more sharpwidth increase may be shorter to achieve the same total change in width.In one embodiment, the form 60 may have a length of 0.5 to 10 inches, orany sub-range therein, such as 1 to 10 inches, 1 to 8 inches, 1 to 5inches, 2 to 8 inches, 2 to 5 inches, or others.

With reference to FIG. 6, a system 100 is shown for splitting fiber tows102. The system 100 may receive a tow 102, or multiple such tows 10. Thetow(s) 102 may be expanded tows that have been separated using thedisclosed methods and systems, above. The tow 102 may be received by thesystem 100 in any suitable way. FIG. 6 shows the tow 102 received viarollers 104, however, others methods may be used, such as a conveyor.The system 100 may include a cutter or chopper 106 to chop the tow 102into shorter tows or segments 108. The shorter segments 108 may have anylength suitable for use in a composite component. In one embodiment, thesegments 108 may have a length of 1 to 100 mm, or any sub-range therein.For example, the segments may have a length of 1 to 75 mm, 5 to 75 mm, 1to 50 mm, 5 to 75 mm, 10 to 75 mm, 20 to 60 mm, 25 to 55 mm, 1 to 2inches, or other sub-ranges. The chopper 106 may be a separatecomponent, or may be incorporated into the rollers 104. The chopper 106may be any device capable of cutting the tow 102. The chopper 106 orchopper materials may vary depending on the type of fiber in the tow,such as carbon fiber, glass fiber, polymer fiber, etc.

After the tow 102 is chopped into shorter segments 108, the segments 108may fall to a receiving surface 110, below. The receiving surface 110may be stationary or it may be moving. For example, the surface 110 maybe a conveyor belt. As a result of falling from the chopper 106 to thereceiving surface 110, the segments 108 may be randomly oriented whenthey land on the receiving surface 110. These segments may betransferred to another system for incorporating the segments into acomposite component, for example, a fiber reinforced SMC component(e.g., carbon fiber). In another embodiment, the receiving surface 110may form part of a SMC process. For example, the receiving surface 110may be a carrier film (e.g., polymer film) having a resin appliedthereon. Therefore, the segments 108 may fall directly onto theresin-carrying film and a second carrier film having a resin appliedthereon may be applied on top of the segments to form a fiber reinforcedSMC material (e.g., carbon fiber). The SMC material may be compacted(e.g., by rollers) and stored for later use, such as on a take-up roll.Alternatively, the SMC material may be transported for immediate orsemi-immediate further processing, such as a molding operation.

Accordingly, embodiments of a system and method for separating a fibertow are disclosed. The fiber tow may be separated or split into a widerand more spread-out tow without mechanically separating the filaments.This may reduce the amount of damage to the filaments during thesplitting process, resulting in higher quality filaments. The fiber towmay be a carbon fiber tow, however, other types of fiber tows may besplit using the disclosed system and method. The disclosed system andmethod may allow carbon tows to be more completely separated thanmechanical methods and may address some of the challenges specific tocarbon tows, such as their generally smaller diameter compared withglass fibers and sizing materials that may be coated on the carbon fibersurface. The disclosed system and method may be used to produce any typeof fiber reinforced component, such as fiber reinforced SMC components.In one embodiment, the system and method may be used to form vehiclecomponents. For example, the system and method may be used to formdecklids, hoods, bumpers, or other parts.

While exemplary embodiments are described above, it is not intended thatthese embodiments describe all possible forms of the invention. Rather,the words used in the specification are words of description rather thanlimitation, and it is understood that various changes may be madewithout departing from the spirit and scope of the invention.Additionally, the features of various implementing embodiments may becombined to form further embodiments of the invention.

What is claimed is:
 1. A system, comprising: a chamber defining firstand second openings and a hollow interior therebetween; the firstopening configured to receive a fiber tow; the second opening beingwider than the first opening; and a vacuum source communicating with thechamber and configured to reduce an air pressure in the hollow interiorand expand the fiber tow.
 2. The system of claim 1, further comprising asealing member extending around the first opening and configured toengage the fiber tow.
 3. The system of claim 2, wherein the sealingmember is made of rubber.
 4. The system of claim 1, further comprising asealing member extending around the second opening and configured toengage the expanded fiber tow as it exits the second opening.
 5. Thesystem of claim 1, wherein the second opening is at least 50% wider thanthe first opening.
 6. The system of claim 1, wherein the second openingis at least 200% wider than the first opening.
 7. The system of claim 1,wherein the first opening has a width of 3 to 20 mm and the secondopening has a width of 5 to 75 mm.
 8. The system of claim 1, wherein awidth of the hollow interior continuously increases from the firstopening to the second opening.
 9. The system of claim 1, furthercomprising one or more hoses coupled to the chamber and the vacuumsource.
 10. The system of claim 1, wherein the vacuum source isconfigured to reduce the air pressure in the hollow interior to 1 torror less.
 11. A method, comprising: pulling a fiber tow having an initialwidth into a first chamber opening, through a hollow chamber interior,and out of a second chamber opening; and reducing an air pressure withinthe hollow chamber interior to separate the fiber tow residing in thehollow chamber interior into an expanded fiber tow having a widthgreater than the initial width.
 12. The method of claim 11, wherein thesecond chamber opening is wider than the first chamber opening andreducing the air pressure within the hollow chamber interior separatesthe fiber tow into an expanded fiber tow having a width that issubstantially the same as a width of the second chamber opening.
 13. Themethod of claim 11, wherein a sealing member extends around a perimeterof the first chamber opening and pulling the fiber tow into the firstchamber opening forms at least a partial seal between the fiber tow andthe sealing member.
 14. The method of claim 11, wherein a sealing memberextends around a perimeter of the second chamber opening and pulling thefiber tow out of the second chamber opening forms at least a partialseal between the expanded fiber tow and the sealing member.
 15. Themethod of claim 11, wherein the reducing step includes reducing the airpressure within the hollow chamber interior to 1 torr or less.
 16. Themethod of claim 11, wherein the reducing step includes reducing the airpressure within the hollow chamber interior using a vacuum hose coupledto the hollow chamber interior and to a vacuum source.
 17. The method ofclaim 11, wherein the reducing step includes reducing the air pressurewithin the hollow chamber interior to separate the fiber tow into anexpanded fiber tow having a width that is at least 100% greater than theinitial width.
 18. The method of claim 11, further comprising choppingthe expanded fiber tow into a plurality of expanded fiber tow segmentsand incorporating the expanded fiber tow segments into a sheet moldingcompound material.
 19. The method of claim 11, wherein the fiber tow isa carbon fiber tow.
 20. A method, comprising: pulling a carbon towhaving an initial width into a first chamber opening, through a hollowchamber interior, and out of a second chamber opening; and reducing anair pressure within the hollow chamber interior to 100 torr or less toseparate the carbon tow residing in the hollow chamber interior into anexpanded carbon tow having a width at least 50% greater than the initialwidth.